1. Field of the Invention
This invention relates to an image processing apparatus formed by interconnecting DSP modules in two or more stages.
2. Description of the Related Art
As an image processing apparatus which can flexibly deal with change in the contents of the image processing and/or addition of contents by only changing the software without changing the circuit boards, there have been known those employing DSP (digital signal processor) modules for signal processing only. The DSP module comprises a signal processor unit which carries out image processing according to program data and a peripheral unit including an input port, a memory and an output port.
In an image processing apparatus employing a DSP module, the overall image processing is generally carried out by one DSP module. When high speed processing is required, the overall image processing is sometimes divided into a plurality of fractions and each fraction of the image processing is carried out by one DSP module. That is, a multi-DSP arrangement is sometimes employed by interconnecting a plurality of DSP modules so that the image processing is carried out by the DSP modules in a pipeline processing (simultaneous parallel processing) system.
For example, when the overall image processing is to be distributed to means A to F as shown in FIG. 14A, functions of means A to F are respectively assigned to DSP modules DSP0, DSP2, DSP4, DSP5, DSP7 and DSP8. Each DSP module carries out designated processing on data input through the input port according to designated program data and outputs processed data through the output port.
In the illustrated example, spare DSP modules are provided for groups of means each surrounded by broken lines in FIG. 14A. More specifically, a spare DSP module DSP1 is provided for the DSP module DSP0, a spare DSP module DSP3 is provided for the DSP module DSP2, a spare DSP module DSP6 is provided for the DSP modules DSP4 and DSP5, and a DSP module DSP9 is provided for the DSP modules DSP7 and DSP8. Normally, these spare DSP modules are caused to operate as data bypass portions which transfers data as-input through the input port to the output port.
When the content of processing by the means A is to be changed, the program data for the DSP module DSP0 is changed. When means G is to be added behind the means A, the program data for the means G is input into the spare DSP module DSP1 and the means G is assigned to the spare DSP module DSP1. When means G is to be added before the means A, the program data for the DSP module DSP0 is changed to the program data for the means G, the program data for the means A is input into the spare DSP module DSP1 and then the means G and A are respectively assigned to the DSP modules DSP0 and DSP1.
In this manner, by employing a multi-DSP arrangement, change in the contents of the image processing and/or addition of contents can be flexibly dealt with by only changing the software without changing the circuit boards.
However, in the image processing apparatus of a multi-DSP arrangement, each DSP module functions as a processing portion corresponding to each means or a data bypass portion, and accordingly, when the means are connected in series, the DSP modules are also connected in series and when the means are connected in parallel, the DSP modules are also connected in parallel. That is, the DSP modules must be connected in the same manner as the means.
Though parallel addition of contents of the processing can be dealt with by connecting in parallel spare DSP modules in a number corresponding to an expected number of parallel processing portions, this approach is disadvantageous in that the size of the circuit becomes too large. That is, in the conventional multi-DSP arrangement, it is difficult to deal with addition of parallel processing with the processing speed kept unchanged without enlarging the circuit size by simply changing the software.
When processing in one or more means becomes unnecessary, the DSP module(s) assigned to the means must be caused to function as a data bypass portion with the DSP module(s) left on the circuit board in vain.